Pipelines are often used for the conveyance of solid/liquid mixtures having a high solid substance constituent, such as, for example settled sludge or mud. Such thick substances have a great internal friction, so that in their pressing through a conveyor pipe no speed gradient develops transversely to the direction of spreading. A relative movement takes place essentially only between the surface of the thick substance strand and the pipe wall, the sliding friction being reduced by the injected lubricant. In the conveyance of partially dehydrated settled sludge, it is already a known
practice (DE-OS 36 05 723), for the reduction of the wall friction to inject at the beginning of the pipe line heating oil, water or an aqueous solution of a high-polymer lubricant between the settled sludge and the wall of the conveyance line. This occurs mostly continuously and proportionally to the conveyance flow in dosed amount with the consequence that between the pipe inner wall and the thick substance strand a boundary layer forms, by which the conveyance pressure can be reduced by 80% and more. However, especially in the case of relatively long conveyance stretches of several hundred meters there are still yielded very high conveyance pressures, since the sliding layer along the conveyance stretch gradually disappears.